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amd64: add a mild depessimization to rep mov/stos users

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Currently all the primitives are waiting for a rewrite, tidy them up in the
meantime.

Vast majority of cases pass sizes which are multiple of 8. Which means the
following rep stosb/movb has nothing to do. Turns out testing first if there
is anything to do is a big win across the board (cpus with and without ERMS,
Intel and AMD) while not pessimizing the case where there is work to do.

Sample results for zeroing 64 bytes (ops/second):
Ryzen Threadripper 1950X		91433212 -> 147265741
Intel(R) Xeon(R) CPU X5675 @ 3.07GHz	90714044 -> 121992888

bzero and bcopy are on their way out and were not modified. Nothing in the
tree uses them.
This commit is contained in:
Mateusz Guzik 2018-06-02 20:14:43 +00:00
parent 2e65567500
commit 15825d5b78
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=334537
1 changed files with 16 additions and 0 deletions
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16
sys/amd64/amd64/support.S
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@ -205,6 +205,11 @@ ENTRY(memmove)
movsq
movq %rdx,%rcx
andq $7,%rcx /* any bytes left? */
jne 2f
movq %r9,%rax
POP_FRAME_POINTER
ret
2:
rep
movsb
movq %r9,%rax
@ -248,6 +253,10 @@ ENTRY(memcpy)
movsq
movq %rdx,%rcx
andq $7,%rcx /* any bytes left? */
jne 1f
POP_FRAME_POINTER
ret
1:
rep
movsb
POP_FRAME_POINTER
@ -269,6 +278,11 @@ ENTRY(memset)
stosq
movq %rdx,%rcx
andq $7,%rcx
jne 1f
movq %r9,%rax
POP_FRAME_POINTER
ret
1:
rep
stosb
movq %r9,%rax
@ -358,6 +372,7 @@ ENTRY(copyout)
movsq
movb %dl,%cl
andb $7,%cl
je done_copyout
rep
movsb
@ -406,6 +421,7 @@ ENTRY(copyin)
movsq
movb %al,%cl
andb $7,%cl /* copy remaining bytes */
je done_copyin
rep
movsb